This invention is generally directed to liquid developer compositions and processes thereof, and wherein there can be generated excellent developed images thereof in, for example, an imaging apparatus, comprising
a support member including a support surface for supporting a layer of marking material;
a marking material supply apparatus for depositing marking material on the surface of the support member to form the layer of marking material thereon;
a charging source for selectively delivering charge species to the layer of marking material in an imagewise manner to form an electrostatic latent image in the layer of marking material, wherein the electrostatic latent image includes image areas defined by a first charge voltage and nonimage areas defined by a second charge voltage distinguishable from the first charge voltage; and
a separator member for selectively separating portions of the marking material layer in accordance with the latent image in the marking material layer to create a developed image, and wherein there is selected as the marking material a liquid developer containing a charge acceptance agent, such as a cyclodextrin, or an aluminum complex, and wherein the developer contains no charge director, or wherein the developer contains substantially no charge director. Preferably, the liquid developer of the present invention is clear in color and is comprised of a resin, a hydrocarbon carrier, and as a charge acceptor a polyethylene oxide-polypropylene oxide, Alohas, an aluminum-di-tertiary butyl salicylate, as illustrated, for example, in U.S. Pat. No. 5,563,015, the disclosure of which is totally incorporated herein by reference, including a mixture of Alohas and EMPHOS PS-900(copyright), a cyclodextrin charge acceptance agent, or charge acceptance additive component, and an optional colorant.
The liquid developers and processes of the present invention possess in embodiments thereof a number of advantages including the development and generation of images with improved image defects, such as smears and hollowed fine features, the avoidance of a charge director, the use of the developers in a reverse charging development process, excellent image transfer, and the avoidance of complex chemical charging of the developer. Poor transfer can, for example, result in poor solid area coverage if insufficient toner is transferred to the final substrate. Conversely, overcharging the toner particles may result in low reflective optical density images, poor color richness or chroma since only a few very highly charged particles can discharge all the charge on the dielectric receptor causing too little toner to be deposited. To overcome or minimize such problems, the liquid toners, or developers, apparatuses, and processes of the present invention were arrived at after extensive research. Other advantages are as illustrated herein and also include minimal or no image blooming, the generation of excellent solid area images, minimal or no developed image character defects, and the like.
A latent electrostatic image can be developed with toner particles dispersed in an insulating nonpolar liquid. These dispersed materials are known as liquid toners, toner or liquid developers. The latent electrostatic image may be generated by providing a photoconductive imaging member (PC) or layer with a uniform electrostatic charge, and developing the image with a liquid developer, or colored toner particles dispersed in a nonpolar liquid which generally has a high volume resistivity in excess of about 109 ohm-centimeters, a low dielectric constant, for example below about 3, and a moderate vapor pressure. Generally, the toner particles of the liquid developer are less than about or equal to about 30 xcexcm (microns) average by area size as measured with the Malvern 3600E particle sizer.
U.S. Pat. No. 5,019,477, the disclosure of which is totally incorporated herein by reference, discloses a liquid electrostatic developer comprising a nonpolar liquid, thermoplastic resin particles, and a charge director. The ionic or zwitterionic charge directors illustrated may include both negative charge directors, such as lecithin, oil-soluble petroleum sulfonates and alkyl succinimide, and positive charge directors such as cobalt and iron naphthanates. The thermoplastic resin particles can comprise a mixture of (1) a polyethylene homopolymer or a copolymer of (i) polyethylene and (ii) acrylic acid, methacrylic acid or alkyl esters thereof, wherein (ii) comprises 0.1 to 20 weight percent of the copolymer; and (2) a random copolymer (iii) of vinyl toluene and styrene and (iv) butadiene and acrylate.
U.S. Pat. No. 5,030,535, the disclosure of which is totally incorporated herein by reference, discloses a liquid developer composition comprising a liquid vehicle, a charge additive and toner pigmented particles. The toner particles may contain pigment particles and a resin selected from the group consisting of polyolefins, halogenated polyolefins and mixtures thereof. The liquid developers can be prepared by first dissolving the polymer resin in a liquid vehicle by heating at temperatures of from about 80xc2x0 C. to about 120xc2x0 C., adding pigment to the hot polymer solution and attriting the mixture, and then cooling the mixture whereby the polymer becomes insoluble in the liquid vehicle, thus forming an insoluble resin layer around the pigment particles.
Moreover, in U.S. Pat. No. 4,707,429, the disclosure of which is totally incorporated herein by reference, there are illustrated, for example, liquid developers with an aluminum stearate charge adjuvant. Liquid developers with charge directors are also illustrated in U.S. Pat. No. 5,045,425. Stain elimination in consecutive colored liquid toners are illustrated in U.S. Pat. No. 5,069,995. Further, of interest with respect to liquid developers are U.S. Pat. Nos. 5,034,299; 5,066,821 and 5,028,508, the disclosures of which are totally incorporated herein by reference.
Lithographic toners with cyclodextrins as antiprecipitants, and silver halide developers with cyclodextrins are known, reference U.S. Pat. Nos. 5,409,803, and 5,352,563, the disclosures of which are totally incorporated herein by reference.
Illustrated in U.S. Pat. No. 5,306,591 is a liquid developer comprised of a liquid component, thermoplastic resin, an ionic or zwitterionic charge director, or directors soluble in a nonpolar liquid, and a charge additive, or charge adjuvant comprised of an imine bisquinone; in U.S. Statutory Invention Registration No. H1483 there is described a liquid developer comprised of thermoplastic resin particles, and a charge director comprised of an ammonium AB diblock copolymer, and in U.S. Pat. No. 5,307,731 there is disclosed a liquid developer comprised of a liquid, thermoplastic resin particles, a nonpolar liquid soluble charge director, and a charge adjuvant comprised of a metal hydroxycarboxylic acid, the disclosures of each of these patents, and the Statutory Registration being totally incorporated herein by reference.
U.S. Pat. No. 4,504,138, the disclosure of which is totally incorporated herein by reference, discloses a method of developing a latent electrostatic charge image formed on a photoconductor surface comprising the steps of applying a thin viscous layer of electrically charged toner particles to an applicator roller preferably by electrically assisted separation thereof from a liquid toner suspension, defining a restricted passage between the applicator roller and the photoconductor surface which approximates the thickness of the viscous layer, and transferring the toner particles from the applicator roller at the photoconductor surface due to the preferential adherence thereof to the photoconductor surface under the dominant influence of the electric field strength of the electrostatic latent image carried by the photoconductive surface, the quantity of toner particles transferred being proportional to the relative incremental field strength of the latent electrostatic image.
U.S. Pat. No. 5,387,760, the disclosure of which is totally incorporated herein by reference, discloses a wet development apparatus for use in a recording machine to develop a toner image corresponding to an electrostatic latent image on an electrostatic latent image carrier. The apparatus includes a development roller disposed in contact with or near the electrostatic latent image carrier and an application head for applying a uniform layer of the wet developer to the roller.
U.S. Pat. No. 5,436,706, the disclosure of which is totally incorporated herein by reference, discloses an imaging apparatus including a first member having a first surface having formed thereon a latent electrostatic image, wherein the latent electrostatic image includes image regions at a first voltage and background regions at a second voltage. A second member charged to a third voltage intermediate the first and second voltages is also provided having a second surface adapted for resilient engagement with the first surface. A third member is provided, adapted for resilient contact with the second surface in a transfer region. The imaging apparatus also includes an apparatus for supplying liquid toner to the transfer region thereby forming on the second surface a thin layer of liquid toner containing a relatively high concentration of charged toner particles, as well as an apparatus for developing the latent image by selective transferring portions of the layer of liquid toner from the second surface to the first surface.
U.S. Pat. No. 5,619,313, the disclosure of which is totally incorporated herein by reference, discloses a method and apparatus for simultaneously developing and transferring a liquid toner image. The method includes the steps of moving a photoreceptor including a charge bearing surface having a first electrical potential, applying a uniform layer of charge having a second electrical potential onto the charge bearing surface, and imagewise dissipating charge from selected portions on the charge bearing surface to form a latent image electrostatically, such that the charge-dissipated portions of the charge bearing surface have the first electrical potential of the charge bearing surface. The method also includes the steps of moving an intermediate transfer member biased to a third electrical potential that lies between said first and said second potentials, into a nip forming relationship with the moving imaging member to form a process nip. The method further includes the step of introducing charged liquid toner having a fourth electrical potential into the process nip, such that the liquid toner sandwiched within the nip simultaneously develops image portions of the latent image onto the intermediate transfer member, and background portions of the latent image onto the charge bearing surface of the photoreceptor.
U.S. Pat. No. 5,826,147, the disclosure of which is totally incorporated herein by reference, discloses a. novel image development method and apparatus, wherein an imaging member having an imaging surface is provided with a layer of marking material thereon, and an electrostatic latent image is created in the layer of marking material. Imagewise charging of the layer of marking material is accomplished by means of a wide beam ion source such that free mobile ions are introduced in the vicinity of an electrostatic latent image associated with the imaging member having the layer of marking material coated thereon. The latent image associated with the imaging member causes the free mobile ions to flow in an imagewise ion stream corresponding to the latent image, which, in turn, leads to imagewise charging of the toner layer such that the toner layer itself becomes the latent image carrier. The latent image carrying toner layer is subsequently developed and transferred to a copy substrate to produce an output document.
U.S. Pat. No. 5,937,243, the disclosure of which is totally incorporated herein by reference, discloses a novel image development method and apparatus, whereby imagewise charging of a toner layer is accomplished by induced air breakdown electrical discharge such that free mobile ions are introduced in the vicinity of an electrostatic latent image coated with a layer of developing material. The latent image causes the free mobile ions to flow in an imagewise ion stream corresponding to the latent image, which, in turn, leads to imagewise charging of the toner layer, such that the toner layer itself becomes the latent image carrier. The latent image carrying toner layer is subsequently developed and transferred to a copy substrate to produce an output document.